Microdetermination of the Thromboxane B3 Gas Chromatography-Selected-Ion Monitoring Using [18O]Thromboxane B3 as an Internal Standard

We devised a simple and effective purification for the microdetermination of thromboxane B₃ (TXB₃), a hydrolysis product of TXA₃. [¹⁸O₂]TXB₃ was synthesized by the repeated base-catalyzed hydrolysis of methyl ester derivatives in [¹⁸O]water, to obtain an internal standard (IS) for the gas chromatography/selected ion monitoring (GC/SIM) of TXB₃. The methyl ester (ME)-methoxime (MO)-dimethylisopropylsilyl (DMIPS) ether derivative was prepared, then GC/SIM was carried out by monitoring the ion at m/z 668 for TXB₃ and that at m/z 672 for IS. A good linear response over the range of 10 pg ∼ 10 ng was demonstrated. We were able to detect the levels of TXB₃ in the medium of human erythroleukemia (HEL) cell cultured with eicosapentaenoic acid (EPA) or docosahexaenoic acid (DHA). This method can be used to determine 3-series thromboxane in biological samples.